Java Reference
In-Depth Information
A
for
loop can be a bit tricky to read until you get used to it. The execution
of the code doesn't follow a “top to bottom, left to right” reading. The increment
code executes after the body of the loop even though it is in the header.
In this example, the initialization portion of the
for
loop header is used to
declare the variable
count
as well as to give it an initial value. We are not required
to declare a variable there, but it is common practice in situations where the vari-
able is not needed outside of the loop. Because
count
is declared in the
for
loop
header, it exists only inside the loop body and cannot be referenced elsewhere.
The loop control variable is set up, checked, and modified by the actions in the
loop header. It can be referenced inside the loop body, but it should not be modi-
fied except by the actions defined in the loop header.
VideoNote
Examples using
for
loops.
For Statement
for
(
;
;
)
Statement
For Init
Expression
For Update
For Init
For Update
Local Variable Declaration
Statement Expression
,
Statement Expression
,
The
for
statement repeatedly executes the specified Statement as
long as the boolean Expression is true. The For Init portion of the
header is executed only once, before the loop begins. The For Update
portion executes after each execution of Statement.
Examples:
for
(
int
value=1; value < 25; value++)
System.out.println (value + " squared is " + value*value);
for
(
int
num=40; num > 0; num-=3)
sum = sum + num;
The increment portion of the
for
loop header, despite its name, could decre-
ment a value rather than increment it. For example, the following loop prints the
integer values from 100 down to 1:
for
(
int
num = 100; num > 0; num--)
System.out.println (num);
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